Gel-forming polysaccharide from psyllium seed husks

Abstract

A purified fraction of the gel-forming component of psyllium seed husks is disclosed, along with process for purification and use of the fraction. The partially purified composition disclosed comprises an arabinoxylan compound comprising a highly branched backbone of β 1,4 linked xylopyranose residues with branches predominantly of xylose, or a trisaccharide consisting of arabinose-xylose-arabinose. The compounds form digestion resistant gels and have laxative and cholesterol-reducing effects.

1 . A compound of Formula I comprising a backbone of β 1,4 linked xylopyranose residues wherein K 1 , K 2 , K 3 , and K 4  are each independently selected from hydrogen, xylose, or a trisaccharide consisting of arabinose-xylose-arabinose; and Z 1  and Z 2  are each hydrogen.  
     
     
         2 . The compound of  claim 1  wherein K 1  and K 2  are each independently selected from hydrogen or xylose and K 3  and K 4  are each independently selected from hydrogen or a trisaccharide consisting of Arabinose-Xylose-Arabinose.  
     
     
         3 . The compound of  claim 1  wherein the trisaccharide has the structure Ara(α1→3)-Xyl(β1→3)-Ara(α1→.  
     
     
         4 . The compound of  claim 3  wherein the trisaccharide has the structure L-Araf(α1→3)-D-Xylp(β1→3)-L-Araf(α1→.  
     
     
         5 . The compound of  claim 1  wherein the arabinose residues are in a furanose ring form and the xylose residues are in a pyranose ring form.  
     
     
         6 . The compound of  claim 1  wherein at least 50% of the total K 1 , K 2 , K 3 , and K 4  are each independently selected from xylose and the trisaccharide Ara-Xyl-Ara.  
     
     
         7 . The compound of  claim 1  wherein at 66% of the total K 1 , K2, K 3 , and K 4  are each independently selected from xylose and the trisaccharide Ara-Xyl-Ara.  
     
     
         8 . The compound of  claim 1  wherein at least 75% of the total K 1 , K 2 , K 3 , and K 4  are each independently selected from xylose and the trisaccharide Ara-Xyl-Ara.  
     
     
         9 . The compound of  claim 1  wherein at least 80% of the total K 1 , K 2 , K 3 , and K 4  are each independently selected from xylose and the trisaccharide Ara-Xyl-Ara.  
     
     
         10 . The compound of  claim 1  wherein about 85% of the total K 1 , K 2 , K 3 , and K 4  are each independently selected from xylose and the trisaccharide Ara-Xyl-Ara.  
     
     
         11 . The compound of  claim 10  which forms a gel in water.  
     
     
         12 . The compound of  claim 11  which resists digestion by intestinal microflora as measured after in an in vitro fermentation simulating in vivo colon fermentation after feeding to humans or rats.  
     
     
         13 . The compound of  claim 1  comprising about at least about 70% xylose and 20% arabinose, and not exceeding 2% galactose.  
     
     
         14 . The compound of  claim 13  which forms a gel in water.  
     
     
         15 . The compound of  claim 14  which is resistant to digestion by intestinal microflora as measured in an in vitro fermentation simulating human colonic fermentation.  
     
     
         16 . The compound of  claim 15  isolated from a plant.  
     
     
         17 . The compound of  claim 16  wherein the plant is  Plantago ovata.    
     
     
         18 . The compound of  claim 17  which has a laxative effect in humans.  
     
     
         19 . The compound of  claim 17  which has cholesterol-lowering activity in humans.  
     
     
         20 . A pharmaceutical composition comprising the compound of  claim 1 .  
     
     
         21 . A method of promoting Taxation in a patient, comprising administering to the patient a laxation-promoting amount of the pharmaceutical composition of  claim 20 .  
     
     
         22 . A method of lowering cholesterol in a patient, comprising administering to the patient the pharmaceutical composition of  claim 20 , in an amount effective to lower the patient's cholesterol.  
     
     
         23 . A gel-forming polysaccharide comprising a backbone structure of β 1,4 linked xylopyranose residues, said backbone structure having branching structures on at least 50% of the O-2 or O-3 positions of the xylose residues, said branching structures comprising xylose or a trisaccharide of Ara-Xyl-Ara.  
     
     
         24 . The gel-forming polsaccharide of  claim 23  comprising at least about 70% xylose and 20% arabinose.  
     
     
         25 . The gel-forming polysaccharide of  claim 24  wherein the xylose residues are in a pyranose form and the arabinose residues are in a furanose form.  
     
     
         26 . The gel-forming polysaccharide of  claim 25  wherein the trisaccharide has the structure Ara(α1→3)-Xyl(β1→3)-Ara(α1→3).  
     
     
         27 . A pharmaceutical composition comprising the gel-forming polysaccharide of  claim 23 .  
     
     
         28 . A method of promoting Taxation in a patient, comprising administering to the patient a laxation-promoting amount of the pharmaceutical composition of  claim 27 .  
     
     
         29 . The method of  claim 28 , wherein the pharmaceutical composition comprises between about 2 and about 6 g, based on dry weight, of the gel-forming polysaccharide.  
     
     
         30 . A method of lowering cholesterol in a patient, comprising administering to the patient the pharmaceutical composition of  claim 27 , in an amount effective to lower the patient's cholesterol.  
     
     
         31 . The method of  claim 30 , wherein the pharmaceutical composition comprises between about 3 and about 7 g, based on dry weight, of the gel-forming polysaccharide.